Indeed, though for SSH only on Android, not iOS, and only with GPG keys not PIV. ConnectBot and OpenKeychain are the apps you need to do this.
Also on Android (but again not on iOS), Chrome (but sadly not Firefox as far as I know yet) can use the google authenticator app (again sadly I think no alternatives to this yet) to speak FIDO with an NFC yubikey.
Also on Android (but again not on iOS), Chrome (but sadly not Firefox as far as I know yet) can use the google authenticator app (again sadly I think no alternatives to this yet) to speak FIDO with an NFC yubikey.